Li Zhong-wei, Ren Ai-min, Guo Jing-fu, Yang Tianxiao, Goddard John D, Feng Ji-kang
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, P. R. China.
J Phys Chem A. 2008 Oct 9;112(40):9796-800. doi: 10.1021/jp8014047.
The first singlet excited state geometries of various isomers and tautomers of firefly oxyluciferin (OxyLH2), as well as their fluorescence spectra in aqueous solution, were studied using time dependent density functional theory (TDDFT). With changing pH in aqueous solution, three fluorescence peaks, blue (450 nm), yellow-green(560 nm), and red (620 nm) correspond to neutral keto and enolic forms, the monoanionic enolic form,and the monocationic keto form respectively. A counterion, Na+, was predicted to cause a blue shift in the fluorescence of anionic OxyLH2. The contributions of a charge transfer (CT) state upon electronic excitation of the planar and twisted structures were predicted. CT was large for the twisted structures but small for the planar ones. The differences between pK and pK* of various oxyluciferin species were predicted using a Forster cycle. A new possible light emitter, namely, the monocation keto form (keto+1), was considered.
利用含时密度泛函理论（TDDFT）研究了萤火虫氧化型荧光素（OxyLH2）的各种异构体和互变异构体的第一单重激发态几何结构及其在水溶液中的荧光光谱。随着水溶液pH值的变化，三个荧光峰，蓝色（450 nm）、黄绿色（560 nm）和红色（620 nm）分别对应中性酮式和烯醇式结构、单阴离子烯醇式结构和单阳离子酮式结构。预测抗衡离子Na+会使阴离子型OxyLH2的荧光发生蓝移。预测了平面结构和扭曲结构在电子激发时电荷转移（CT）态的贡献。扭曲结构的CT较大，而平面结构的CT较小。使用福斯特循环预测了各种氧化型荧光素物种的pK和pK*之间的差异。考虑了一种新的可能的发光体，即单阳离子酮式结构（keto+1）。
